Ok so i got 2 new front tires on my moms vehicle (2001 toyota sienna) and i noticed afterward that the brakes felt very soft, way more than normal. It is slow to stop and i have to push the pedal almost to the floor for it to stop. I'm not sure what could have happened when the tires were changed that could cause this? At first i thought it was a coincidence so i took it to a brake shop and the brakes were replaced brand new and the guy also bled the brakes. However i am still having the spongy brake issue. Sometimes if i pump the brakes it will feel firm again but I'm still having the spongy brakes consistently. Any ideas on what this could be? Could the tire shop have done something incorrect when putting the new tires on? I'm not sure if the car is safe to drive. Thanks.
The tires themselves have nothing to do with the feel of the brakes (unless the tires are falling apart), and replacing the tires isn't likely to harm the brakes in any way, so I'll agree with your guess that it's coincidence.
As to the cause, if you don't have air in the lines (which bleeding will check), and your brake fluid reservoir is properly filled, then you may have an issue with the master cylinder. 17 years is a good long life for a car, and wear and tear alone could easily cause the master cylinder to fail. That said, replacing a master cylinder may be beyond a "brake shop"; you may have to take it to a full-service repair shop to diagnose and/or fix it.